They can run old, outdated raids. Since the design of blue mage is that it will be a soloist job and not suited to groups, there is little reason to believe that will ever change for them. There is ample reason to believe the alternative, that it will be locked out of challenging content forever.

Keep in mind that they brought up a specific scenario of the Blue Mage casting Lv5 Death on a raid boss being a reason why they couldn't implement it as a normal job.

The only reason they would change it is if we ask them to.